Such is the case of today’s pen—a Double Flow Fountain Pen. Apparently, it is just a BCHR pen in the very traditional shape of Japanese eyedroppers, often called Onoto shape. Usually, the tail operated the shut-off valve. But that is not the case of this pen.

The engraved marks on the section are similar to those of a hoshiawase pen.

The pen has two concentric ink deposits--the innermost is attached to the section on the picture. The ourtermost is the barrel (on the background), as is the case on all eyedropper pens.

On this picture, both deposits are dettached from the section.

This pen is still an eyedropper, but it lacks any shut-off valve. In exchange, it has two concentric ink deposits inside the barrel, and the section has separate channels for each deposit. On the outside, the gripping section has some engraved marks—similar to those in a hoshiawase pen—to select the deposit from which the ink would feed the nib. Three are the options: outer, inner, and a mixture of both. Needless to say, the inks used with this pen had to be compatible; that is, mixable as the mixture would take place directly in the feed.

This picture shows the back of the section. The wider thread attaches the barrel; the smaller, the inner deposit for the second ink. Two feeding holes are visible--the central for the innermost deposit, and the lateral one for the outer reservoir.

The Double Flow Fountain Pen together with a copy of the instruction sheet.

In summary, this Double Flow Fountain Pen, such was its name, is a dual eyedropper with an ink selecting mechanism. Very few units of it are known, and on the one here shown, the nib is a later replacement. There exist, however, some instruction sheets. On it, the manufacturer explains that this dual flow system had been patented in Japan (patent number 36005), and that applications had been filed for patent in Britain, USA, France, and Italy. It dates back from the mid 1920s.